Brain and Spinal Tumors Health Article

Demographics

Brain and spinal tumors occur in people of all races and sexes, but are slightly more common in Caucasian people than other races. About 40,000 people are diagnosed with a brain tumor each year in the United States. Overall, brain tumors tend to occur more frequently in males than females. Meningiomas, however, occur more frequently in females. Most brain tumors occur in people over 70 years of age, and most brain tumors in childhood occur before age eight. Brain and spinal cord tumors in children are the second most common form of childhood cancer, with about 1,500 children developing these tumors each year. Family history may be predictive, especially with regard to chromosomal abnormalities or changes that may result in the loss of tumor suppressor genes. People with family members who have glioma may be at higher risk of developing a brain tumor.

Long-term exposure to certain chemicals may increase the risk of developing a brain tumor. People exposed to acrylonitrile and vinyl chloride while manufacturing some textiles and plastics, pathologists exposed to formaldehyde, and workers in the nuclear industry may all be at higher risk of developing malignant brain tumors.

Almost 10,000 Americans are diagnosed each year with a spinal cord tumor. Primary spinal cord tumors are rare; most are the result of metastasis (spread) from another site of primary cancer in the body. Most primary spinal tumors are not malignant, but as they occupy space surrounding the spinal cord, they may cause pain and disability.

Causes and symptoms

With the exception of a few genetic syndromes associated with tumors of the brain and spinal cord, the cause of primary nervous system tumors remains a mystery. As most malignant brain tumors are secondary tumors that result from primary cancer that has spread from elsewhere in the body, factors known to influence the development of other cancers, such as smoking, may be considered related causes.

Although not all of the molecular mechanisms are fully understood, there have been dramatic advances in understanding the causes of the cellular transformations of normal healthy cells into tumor cells (tumorigenesis) within the brain.

Present molecular models identify specific genes that play a role regulating the cell cycle and that data indicate that they play a role suppressing tumor growth (tumor suppressor genes such as the p53 gene). Damage to the gene or loss of the chromosome on which it resides (chromosome 17) correlates to the initiation of astrocytoma tumorigenesis. Oncogenic viruses that interfere with tumor suppressor genes have also been linked to tumor formation. More research is needed into the mechanisms of tumor cell transformation before a definitive link can be established.

Other potential causes of brain or spinal cord tumor development under investigation include head injury, occupational exposure to chemicals, and viruses. Additionally, scientists continue to research the possibility of a relationship between cell phone use and malignant tumors of the central nervous system. As of mid-2004, no relationship has yet been established between cell phone use and increased rates of brain cancer.

Symptoms of brain tumors include headaches, nausea, vomiting, seizures, and disturbances in vision and hearing that cannot be related to a disorder of the external sensory organs. Changes in personality and developmental problems, motor problems, and balance problems are also characteristic of tumors.

Spinal cord tumor symptoms often include pain, invalid sensory inputs such as numbness in the toes, feet, or legs, and motor coordination problems.

Diagnosis

Brain and spinal tumors may be diagnosed by a combination of neurological examination and imaging such as magnetic resonance imaging (MRI) scans, computed tomography (CT) scans, and positron emission tomography (PET). Other diagnostic tests include laboratory tests (including blood and spinal fluid analysis), myelography, radionucleotide bone scan, biopsy, and microscopic examination of tissues.

Brain and spinal tumors are usually confirmed by computerized axial tomography (CAT) scan, or via the more accurate MRI or PET scans.

MRI scans provide the ability to image and anatomically pinpoint tumors of the brain and spinal cord and thus

provide accurate diagnosis without surgery. Both the MRI and CAT scans produce segmental images of the brain that allow physicians to determine the location and extent of tumors, as well as the extent of damage to neural or surrounding tissue. PET scans use a glucose-and-tracer mixture that is injected into the bloodstream to form a picture of metabolic activity of the brain. As tumor tissue uses more glucose than normal tissue, the tumor presents a brighter image than normal tissue in the picture generated by the scan.

At the tissue level, the presence of cell division at the time of histological examination (tissue exam) is indicative of a higher grade tumor. The greater the rate of mitotic activity (cell division), usually the greater potential for a tumor to advance to a higher and more dangerous type.

GBM tumors are characterized by densely packed cells and the highest high rates of mitotic division. Other tumors such as other gliomas and astrocytomas are diagnosed on the bases of histological examination.

Tumors of the human brain and spinal cord can also be differentiated based on molecular genetic studies that link specific changes in tumors to underlying chromosomal and gene changes (e.g., inactivation of a particular tumor suppressor gene).